import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User:
 * Date: 2025-09-25
 * Time: 23:49
 */
public class demo1 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] cost = new int[n];
        int[] dp = new int[n+1];

        for (int i = 0; i < n; i++) {
            cost[i] = sc.nextInt();
        }

        for (int i = 2; i <= n; i++) {
            dp[i] = Math.min(dp[i-1]+cost[i-1], dp[i-2]+cost[i-2]);
        }
        System.out.println(dp[n]);
    }
}
